Re: [Nolug] Fastest way to create a local mirror of a huge tree?

On Fri, Sep 9, 2011 at 9:53 AM, Jerry Wilborn <jerrywilborn@gmail.com> wrote:
> What would cause the data to be garbled?

Unless you unmount or remount the source file system read-only before
using it as a source for the DD,
you are not really assured to get a consistent or even valid
filesystem on the target device.

If there are any changes on the source filesystem while your DD is in
flight, the filesystem written to the
target may be corrupt in this manner; the copied filesystem might
include _some_ of the changes
that occured while the DD was in flight but not all of the changes.

For example... you might copy an inode referring to a block that
does not actually exist
(because an earlier version was already copied from a lower numbered
sector of the volume)

In many cases deactivating or making the source of a copy/backup
read-only might be unacceptable.

--
-JH
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